1. Field of the Invention
This invention relates to a system and method for compressing a video data set, and more particularly, to a system and method for providing a coding strategy provided with parameter searching for better performance in a target bit rate.
2. Description of the Related Art
It is well known that a bitstream produced by H.264/AVC, the most important developments in video coding to date, achieves a significant improvement in compression efficiency compared to previous coding standards, such as MPEG-2, H.263, and MEPG-4. A number of features contribute to the success of H.264/AVC; for example, the adoption of various prediction modes, and the improved rate-constrained control achieved by using a Lagrangian bit-allocation technique.
Since using more prediction modes increases the number of coding options, the improvement in prediction accuracy is achieved at the cost of increasing the complexity of obtaining optimal coding parameters. Furthermore, the amount of side information required to transfer the chosen modes also increases. H.264/AVC employs a rate-constrained Lagrangian optimization method. The motion estimation process searches for the motion vector minimizing the Lagrangian cost function prior to performing residual coding. However, although this is a practical solution, it is not an optimal way to select a motion vector.
Referring to FIG. 2, motion vectors A 202 and B 204 generate the same amount of distortion, but A 202 requires more bits. According to the Lagrangian cost function, the B 204 vector is chosen to encode the block, but the selection is obviously not optimal for all bit-rates. The optimal solution is to choose motion vector A 202 at smaller bit-rates, and motion vector B 204 at higher bit-rates.
To obtain the optimal performance of all bit-rates, the residual coding must not be neglected during motion vector selection. Therefore, a non-Lagrangian-based technique is proposed that incorporates the residual coding of various modes into the rate-distortion costs, the projected cost, and yields a labeled R-D curve. The mode that should be chosen to optimally encode a block at a specific bit-rate can be identified from the label on the curve.
In view of this, an improved encoding strategy is needed. The proposed encoding strategy is characterized in that the an encoding system that constructs coding strategies into tree-based representation to search a parameter set for encoding the data set based on the projected cost of using the coding strategies in a constrained rate.